Updated, 7:24 p.m.: As of the end of the day, McCaskill says 53 senators have signed the letter.
Sen. Claire McCaskillClaire McCaskillMcCaskill: I wonder if people voting for Trump are embarrassed VA opposes bill aimed at helping vets in mustard gas experiments Blame game begins on Zika funding MORE (D-Mo.) said Wednesday she has half the Senate on board with her effort to end senators' anonymous holds on nominations.
McCaskill said she now had 50 senators who had signed the letter she has been circulating pledging to end the use of the practice, in which one senator can object, without giving his or her name, to any nominee moving forward.
McCaskill tweeted Wednesday:
Now have 50 signatures on End the Secret Hold letter.More work on it today.Rules being broken by failure of Rs to reveal who's holding noms.
McCaskill said, too, in a conference call with Missouri reporters Wednesday that she's hopeful she can win a 60-vote, filibuster-proof majority on reform.
"We've crossed the majority -- we haven't gotten to 60, yet I'm feeling confident that we will get to 60," she said.
The Missouri centrist has been leading the charge against the practice, arguing it has been used to some effect by Republicans in the minority to stall or stop President Barack ObamaBarack ObamaSocial Security to run dry three years sooner than expected: study Former CIA chief shuts down Trump's calls for waterboarding Clinton camp: Trump's fundraising 'bragging is total bunk' MORE's nominees.
Senate Majority Leader Harry ReidHarry ReidIowa poll: Clinton up 14 on Trump, Grassley in tight race with Dem Lynch meeting with Bill Clinton creates firestorm for email case The Hill's 12:30 Report MORE (D-Nev.) railed against the practice of secret holds on Tuesday, suggesting the matter might be referred to the Senate Ethics Committee at some point.
Updated at 12:58 p.m.